1. Field of the Invention
The invention relates in general to an input module for an electronic device and in particular to an input module with a touch sensing unit for an electronic device.
2. Description of the Related Art
Referring to FIG. 1A, US patent publication No. US20040077373 A1 discloses a conventional portable radiotelephone 100 comprising a keypad assembly 110 and a display 120. The keypad assembly 110 comprises a plurality of key buttons for data input. Specifically, the keypad assembly 110 can function as a touchpad. As shown by the character “A” in FIG. 1, the user can input characters by handwriting on the keypad assembly 110.
Referring to FIG. 1B, the keypad assembly 110 comprises a circuit board 111, a plurality of metal domes 112 on the circuit board 111, a capacity sensor 113, a keypad rubber 114, and a plurality of bosses 115 and key buttons 116. The capacity sensor 113 connects the keypad rubber 114 and the key buttons 116. The bosses 115 project downward from the key pad rubber 114 to press the metal domes 112. The user can input data by directly pressing the key buttons 116 or handwriting thereon.
Conventionally, the capacity sensor 113 is disposed beneath the key buttons 116 for detecting objects (such as user's fingers) over the keypad assembly 110. To facilitate precise sensitivity and reduce distance between the object and capacity sensor 113, the key buttons 116 are preferably flat and thin. However, since the capacity sensor 113, the keypad rubber 114 and the key buttons 116 are thin and tightly bonded, it is difficult to accomplish click feeling and haptic feedback when pressing the key buttons 116.